1. Place your chosen image here. The four corners must just cover the arrow tips. For covers, the three pictures should be the same size and in a straight line. Venting Controllers/Positioners – understanding natural gas emission rates

2. 2 Background  Emissions of natural gas from gas networks originate from a number of sources including:  Infrastructure failure  Operational/process venting  Fugitive leakage from pipeline infrastructure  Fugitive leakage can be a significant, continuous emission  Valves, flanges, connectors, pressure relief devices, PIG trap doors and filters have been identified as major fugitive emission sources.  Venting from some process control equipment can also be significant and continuous  A new project has been initiated to evaluate the emission from valve controllers and positioners

3. 3 Venting Controller Project - Outline  National Grid initiated an R&D project to:  Identify and quantify the gas venting from selected controllers and positioners  Develop a robust test methodology  Identify the controller types and suitable sites for test work  Perform lab tests on selected controllers and positioners to understand the impact of supply pressure on vent rate  Study the venting at a number of sites to get a representative range of controller types and operation  Measure the vent emission rates using a high flow sampling technique, for short term measurements – time averaged data  Study how the vent rate varies as a function of controller operation (by studying the vent rate as a function of time over a 24hr period)  Install suitable flow meters on selected vents – to establish time-dependence of vent rate  Compare the vent rate profiles with site operational parameters to determine if there is any correlation  Undertake two or three measurement campaigns at different times of the year to check whether system operation factors influence the emission rate

4. 4 Venting Controller Project - Targets  The key target outputs from this project include:  Quantify the vent emission rate from selected controllers and positioners  Study how the vent rate varies as a function of site operation (looking at time and seasonal dependence)  Determine if there is a link between the emission rate and site operation (or not)  Couple site infrastructure information with measured emissions to estimate overall emission inventory  Identify controllers and positioners that give better (ie. lower) emission performance  Evaluate potential emissions reductions through retro-fit of different controllers and positioners.

5. 5 Venting Controller Project – Initial Results  Site survey controller emission rates.  11 AGI sites surveyed and vent emission rates measured using high flow sampling system – “Snap shot” measurements taken on an “as found” basis  Emission rates measured for Bristol Babcock, Fisher, Neles, Taylor, Mokveld, ABB, Watson & Smith and Becker (pneumatic valve controllers and positioners)  3 sites selected for longer term testing.  Laboratory-based testing on different controllers and positioners.  Linear relationship of emission rate with controller or positioner pressure observed (for Fisher positioner and Bristol Babcock controller).  Longer-term emission rate measurement method development  Selection of suitable flow meter – microturbine flow meter option selected to match the pressure and flow characteristics of the vent emission  Method optimised in the laboratory and high flow sampling approach tested alongside this method – good correlation  Method tested at two sites (short-term test)  Longer-term emission test campaign  Planning underway; Ancillary equipment sourced; Operational issues addressed.

6. Impact of supply pressure (Bristol Babcock controllers)  Operating manual proposes a controller pressure of 20psi  Site observations suggest controller pressure may be higher  Up to 70psi possible  Between 20 – 40psi observed on the snap-shot surveys.  Linear relationship of emission rate with controller pressure  Confirmed manufacturer quoted discharge rate of 0.05cfm at 20psi  Emission rate up to around 0.09cfm at 40psi  [0.05cfm ≈ 0.085 m 3 /h (≈ 0.5 t/a per controller)] 6

7. Impact of supply pressure (Fisher Positioners)  Operating manual proposes a positioner pressure of 100psi  Site observations suggest positioner pressure may be between 40 – 150psi  Linear relationship of emission rate with controller pressure (limited range of lab tests)  Extrapolation of lab tests Confirms manufacturer quoted discharge rate of 0.3cfm  If average positioner pressure is 100psi then vent emission rate will be around 0.5 m 3 /h (≈ 3 t/a per positioner)] 7

8. 8 Next steps  Install Becker controller in laboratory and determine typical vent emission rates (Target date: February 2013)  Obtain a new Fisher positioner and extend the laboratory study on pressure variation of vent emission rate (Target date: March 2013)  Undertake the first long-term test campaign at three selected sites (Target date: March 2013)  Study the emission rate variation as a function of site operational parameters (overall site flow, gas temperature and pressure) (Target date: April 2013)  Fine tune the long-term test study, based on the first campaign to optimise data gathering for the second (and possible third) campaign (Target date: April-May 2013)